In a photolithography process in the manufacture of semiconductor devices, predetermined resist patterns are formed on a semiconductor wafer (hereinafter, referred to as a wafer) by sequentially performing the following processes: a resist coating process for applying a resist liquid on the wafer to form a resist film; an exposure process for exposing a predetermined pattern in the resist film; a post exposure baking process (hereinafter, referred to as a PEB process) for heating the wafer in order to promote a chemical reaction in the resist film after the exposure process; and a developing process for developing the exposed resist film.
In recent years, a chemically amplified resist has been widely used in the aforementioned formation of resist patterns. The chemically amplified resist produces acid when exposed. Such acid is diffused through the PEB process and progresses to a chemical reaction in the resist, thereby changing the solubility of an exposed region to a developing liquid.
Further, in the aforementioned exposure process, a light source, which outputs a KrF laser (wavelength: 248 nm), a ArF laser (wavelength: 193 nm), a F2 laser (wavelength: 157 nm) or the like, is used as an exposure light source. The exposure process is performed by irradiating this laser to the resist film on the wafer. In this case, in the PEB process to be performed after the exposure process, the wafer is heated at a heating temperature of, for example, 110° C. or 90° C. for sixty seconds (for example, see Japanese Laid-Open Patent Application No. 2005-221801).
Meanwhile, to achieve still higher integration of semiconductor devices, a resist pattern to be formed on a wafer has become more and more minute. For this reason, it has been considered to use a light source which outputs a light having a wavelength shorter than the KrF laser, the ArF laser and the F2 laser (for example, an EUV (Extreme Ultra Violet) having a wavelength of 13 nm to 14 nm) as the exposure light source of the aforementioned exposure process.
However, a light amount of an EUV light source, which is used in a so-called EUV lithography performing an exposure process by means of an EUV, is significantly low in comparison with conventional exposure light sources. Thus, when performing the PEB process by the above-explained conventional methods, the acid produced from the resist for EUV is not easily diffused and therefore the chemical reaction in the resist does not easily progress. Accordingly, forming a resist pattern in a resist film for EUV on a substrate using the conventional methods leads to reduction in the throughput of a wafer process.